Method of consolidation of incompetent subsurface formations



Feb. 6, 1968 1. w. JENNlNGs ET AL 3,367,420

METHOD OF CONSOLIDATION OF INCOMPETENT SUBSURFACE FORMATIONS Filed March 7, 1966 Pkg. 6

United States Patent 3,367 420 METHOD F CONSOLIDATION 0F INCOMPETENT SUBSURFACE FORMATIONS James W. Jennings, Verona, John Papala, Apollo, and

Francis M. Smith, Gibsonia, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Mar. 7, 1966, Ser. No. 532,424 5 Claims. (Cl. 16627) This invention relates to the production of gas and oil from an incompetent subsurface formation, and more particularly to a method of placing a packing material in a cavity formed in said formation and consolidating said packing material into a coherent permeable mass.

As is known, the particles comprising the formation of many gasor oil-bearing formations, are not eifectively cemented together and therefore the formation is either substantially unconsolidated or only loosely consolidated. When fluids are produced from such formations, solid particles of the formation ow into the well. Hence, these formations are frequently referred to as incompetent formations. If the formation fluids in incompetent formations are under high pressure, the particles of the formation will flow through the tubing and other equipment in the well, at relatively high velocities causing severe erosion of the tubing, valves and other equipment in the well. On the other hand, when the flow rates are of such low order that the formation particles cannot be conveyed through the tubing and out the well, the particles of the formation ow into the well and plug the tubing. It is then necessary to perform expensive work-over operations on the well to place the well in operation. In extreme cases, the incompetent oil-bearing formation surrounding the well is washed out and undermines the overlying formations penetrated by the well with the result that the overlying formations sometimes collapse and damage the well.

It is imperative then that some means for propping or restraining the motion of the formation particles be provided, prior to placing the well in production, to avoid the above-described diculties. Many methods have been proposed for preventing movement of sand into a well. In one such method, a slotted liner is set in the well and formation fluids are produced through the slots in the liner. In another method, a gravel packing operation is combined with the setting of the liner. In gravel packing operations, sand or other aggregate material is packed around the liner to provide support for the formation particles. The biggest disadvantage of these methods lies in the fact that the formation particles are still free to move and consequently they can plug the gravel pack or the slotted liner. Furthermore, the setting of liner and gravel packing require several round trips into the well and therefore are relatively expensive methods of completing a Well.

In still another method, a liquid, capable of setting to form a resin, is displaced outwardly into the formation which coats the formation particles and thereafter is caused to set and form a resin which bonds the particles together. These settable liquids are relatively expensive and large quantities of the liquids are required to bond formation particles for a distance into the formation sufficient to prevent movement of the formation particles. Another disadvantage of using these settable liquids lies in the fact that it is di'icult to determine, in advance, how far into the formation the liquid must penetrate in order to restrain movement of the formation particles.

Accordingly, as an overall object, the present invention seeks to provide a method of consolidating incompetent subsurface formations.

Another object of the invention is to provide a method 3,367,420 Patented Feb. 6, 1968 of consolidating incompetent subsurface formations by which positive placement of the packing material within the formation cavity is assured and whereby improved ilow rates immediately adjacent to the casing perforations result.

A further object of the invention is to provide a method of consolidating incompetent subsurface formations, which at its completion, leaves the casing free of obstructions.

The present invention resides in a method of consolidating an incompetent subsurface formation surrounding a well by selectively injecting a packing material through multiple perforations in the casing, into a cavity washed in the formation and retaining the particles in the cavity until such time as the cavity is packed. Thereafter, the packing material is caused to consolidate into a coherent permeable mass which restrains motion of the particulate matter of the formation while permitting the liquid or gaseous medium of the formation to flow into the well for the purpose of recovering the same.

In accordance with the present invention, the casing is perforated at vertically spaced locations to provide at least one small perforation and at least one large perforation. A packer is set in the region between the perforations and tubing run through the packer whereby one of the perforations communicates with the annular space between the tubing and the casing and the other perforation communicates with the interior of the tubing. A cavity is washed in the subsurface formation by pumping a washing liquid through one of the perforations into the formation whereby a quantity of the particulate matter of the formation is carried out through the other perforation. A uid containing a permeable sealer member is then pumped through the larger perforation to lodge the permeable sealer member in covering relation with the small perforation at a location externally of the casing, that is, within the cavity. A calculated quantity of packing material in the form of particles is suspended in a liquid to form a slurry and the slurry is pumped into the cavity. The particles agglomerate about the permeable sealer member and ll the cavity while the conveying liquid passes through the permeable sealer member. Thereafter, the particles are consolidated into a coherent permeable mass which lls the cavity and through which the liquid or gaseous medium of the formation may flow without passage of the particulate matter of the formation. The particles are preferably precoated with a settable coating containing a curing agent whereby after packing in the cavity, the coating sets to bond the particles into a coherent permeable mass. Alternatively, a settable liquid and a curing agent may be sequentially introduced into the particles, after packing and permitted to set and bond the particles into a coherent permeable mass.

The above and other objects of the invention will become apparent from the following detailed description by reference to the accompanying drawings, in which:

FIGURE l is a sectional view, illustrating the perforation of the casing;

FIG. 2 is a sectional view, illustrating a washing step in which a cavity is formed in the incompetent subsurface formation;

FIG. 3 is a sectional view, illustrating the introduction of permeable sealer members into the cavity;

FIG. 4 is a sectional view, illustrating packing material agglomerating about the permeable sealer members and filling the cavity;

FIG. 5 is a fragmentary sectional view, illustrating the placing of impermeable sealer members to prevent backtlow during consolidation of the packing material;

FIG. 6 is a sectional view, illustrating a coherent permeable mass surrounding the casing at the completion of the present method; and

FIG. 7 is a sectional view, on a reduced scale, illustrating the formation of a second coherent permeable mass at a new location within the incompetent subsurface formation.

Referring now to FIGS. 1-5, inclusive, there is illustrated a well bore 1f) which is drilled from the surface of the earth to penetrate a plurality f subsurface intervals, zones, horizons, strata, formations, sands, and the like, which are designated herein by the numerals 12, 14 and 16. For the purpose of describing the present invention, the subsurface formation 14 is a gasor oil-bearing formation, otherwise termed a producing formation, wherein the formation particles are either substantially unconsolidated or only loosely consolidated. The subsurface formation 14 is therefore known as an unconsolidated subsurface formation which cannot be worked efiiciently, in its natural state, to produce the liquid or gaseous medium of the formation. As explained above, the formation 14 requires the installation of a coherent permeable mass which will restrain motion of the formation particles while permitting the liquid or gaseous medium of the formation to flow into the well bore and be recovered. The method of the invention comprises certain steps which will now be described by reference to FIGS. 1-5, inclusive.

Referring now to FIG. 1, the well bore 10 has casing 18 secured therein by cement 20. A perforator 22 resides within the casing 18 and, for the purposes of illustration only, may comprise a shaped charge perforator. As is conventional, the perforator 22 is lowered through the casing 18 by a wire line 24 and is positioned at the desired level within the region of the unconsolidated subsurface formation 14. The perforator 22 is then fired to form at least one and preferably a plurality of circumferentially spaced, small perforations 26 at one level in the casing 18, and at least one and preferably a plurality of circnmferentially spaced, large perforations 28 at a lower level in the casing 18. The perforations 26, 28 penetrate the casing 18 and the cement 20, into the formation 14 and, in actual practice, would be spaced apart by a distance of from about two feet to about four feet.

After the perforations 26, 28 have been formed, the perforator 22 is removed and tubing 30, as shown in FIG. 2, is lowered into the casing 18. A packer 32, carried by the tubing 30 and being, for example, of the inflatable type, is set in the region between the perforations 26, 28. The tubing 30 and the casing 18 define an annular space 34 which communicates with the small perforations 26. The tubing 30 is provided with a plurality of apertures 36 which are positioned below the packer 32 and which communicate with the large perforations 28. At this time, a washing liquid, such as salt water, is pumped down the annular space 34 and circulated through the small perforations 26, into the formation 14 to wash away a quantity of the particulate matter of the formation 14 through the large perforations 28 and apertures 36 up through the tubing 30, as indicated by the arrows. Circulation of the washing liquid is continued until such time as a cavity 38 is formed in the formation 14. The size of the cavity 38 should be at least one-half cubic foot and preferably about three cubic feet.

The washing liquid is pumped into the cavity 38 at a relatively low pressure so that the region of the formation 14 immediately adjacent to the cavity 38 is not saturated with the washing liquid. That is to say, the pressure of the washing liquid is low enough that it will not penetrate the formation 14 and therefore will not reduce the amount of pore space available through which the liquid or gaseous medium of the formation 14 will subsequently iiow.

After the desired cavity size has been washed out, as indicated by the quantity of debris collected at the surface, permeable sealer members 46 are introduced into the washing liquid and conveyed thereby through the large perforations 28, into the cavity 38 and lodged in the small perforations 26, as illustrated by the permeable sealer member 40A in FIG. 3. The permeable sealer members 40 are preferably in the form of a ball which has a plurality of perforations provided therein or which is formed from permeable material. The permeable sealer members 40 may comprise, for example, those permeable ball sealers described and illustrated in U.S. Patent No. 2,933,136, issued to Earl D. Ayers and James W'. Rebbeck.

The permeable sealer members 40 are small enough to pass through the large perforations 28 but large enough so that they will be lodged against the small perforations 26 and be retained therein by fluid action. The permeability of the sealer members 40 permits the etiiux of the washing duid therethrough into the annular space 34. As the permeable sealer members 46 are lodged against the small perforations 26, an increase in circulating pressure will be noted at the surface, whereupon a packing material 42, in the form of granular particles, is injected into the liquid and pumped down the tubing 30, as illustrated in FIG. 3.

Referring now to FIG. 4, the packing material 42 is conveyed through the large perforations 28, into the cavity 38 and into contact with the permeable Sealer members 40. The size of the pore spaces in the permeable sealer members 49 and the size of the particles of the packing material 42 is such that the particles of the packing material will agglomerate about but-not plug the permeable sealer members 40 and fill the cavity 38. The required quantity of packing material may be determined from the quantity of debris collected at the surface during the washing step. An additional quantity of packing material may be added to the initially determined amount as allowance for additional cavity enlargement caused by the fluid circulation necessary to firmly place the packing material 42 in the cavity 38.

The packing material 42 is in the form of particles which preferably comprise 35-mesh or smaller hard glass beads. Alternatively, the particles could, instead, comprise other granular or particulated solids, such as, sand, ground nut hulls, sco-ria or the like. Although not limited thereto, the particles can be treated in accordance with the teachings of U.S. Patent No. 3,123,137, issued to Bill M. Young, John M. Knox and Roger F. Rensvold, wherein a resin coating, such as, a linear polyester resin, is applied to the surfaces of the particles. The resin coating is capable of setting to bond the particles into a coherent permeable mass having a strength sufficient to restrain motion of the particulate matter of the formation 14 while having a permeability which permits the liquid or gaseous medium of the formation 14 to ow therethrough without passage of the particulate matter of the formation 14. Other resinforming coatings, such as, urea-formaldehyde mixtures, furfural and its derivatives and epoxides would be equally suitable and may be preferred.

For a detailed description of the process for treating particles and of the materials preferably employed, reference is made to the aforesaid U.S. Patent No. 3,123,137. For the purposes of the present invention, howevr, it will be sufficient to state that the particles are pretreated with a surface conditioning agent which improves the affinity of the surfaces to be coated for the resin coating subsequently applied. Thereafter,the particles are coated with a linear polyester or other suitable resin. A setting or curing agent may be incorporated into the resin composition or may be added after the particles have been placed in the cavity 38. As an example, the particles may be pretreated with styrene and subsequently coated with polyester resin, such as Naugatuck Chemical Companys Vibrin X-1058 containing cobalt naphthenate and Lupersol D.D.M. as curing agents.

In carrying out the method of the present invention, the surface conditioning agent and the resin-containing cornposition may advantageously be applied at or near the well site. The materials should be thoroughly mixed to 0btain as nearly as possible a uniform film r coating covering the surfaces of the particles. As is conventional, a mechanical or other stirring or blending device may be employed to agitate and mix the liquid and particles together. Where a curing agent for the resin is included in the coating composition, it will ordinarily be desirable to delay mixing together of the resin and curing agent until just prior to coating the particles. The resin-coated particles may then be added without delay to the carrying Huid to form a slurry which is pumped down the tubing 30 into the cavity 38 prior to the coating on the partieles reaching a set or hardened condition.

Although a resin-forming composition is preferred, it will be readily apparent that other settable coatings, such as various cement compositions, may be employed to advantage.

After the packing material has been placed in the cavity 38, impermeable sealer members 44, shown in FIG. 4, are conveyed down the tubing 30. As shown in FIG. 5, the impermeable sealer members 44 are lodged in the apertures 36 in the tubing 30 so as to seal the same and thereby prevent backflow during consolidation of the packing material 42. A predetermined length of time is allowed to lapse during which the settable coating of the packing particles sets to bond the particles into a coherent permeable mass.

Thereafter, as shown in FIG. 6, the packer 32 may be released and the tubing 30 elevated whereupon the packer 32 is reset above the upper perforations. At this time, the liquid or gaseous medium o-f the formation 14, illustrated by the plurality of arrows, may be caused to flow through both the small perforations 26 and the large perfor-ations 28 and recovered at the surface. It is to be noted that the well bore is free of obstructions which ordinarily redue the flow rate of the formation medium.

As illustrated in the drawings, the cavity 38 has a toruslike configuration, that is, the cavity 38 surrounds the well bore 10. This configuration is the direct result of providing a plurality of perforations 26, 28 which are circumferentially spaced around the casing 18. Although those perforations 26, 28 visible in FIG. l for example, are shown residing in the plane of the drawings, it may be desirable to form the perfor-ations such that none of the perforations 26, 28 reside in the same vertical plane. The cavity subsequently produced would also have a toruslike configuration. Although a plurality of the small and large perforations is preferred, it is also possible to form a cavity in the incompetent formation by using only one small perforation and one large perforation. In this instance, satisfactory results are obtained when the perforations may lie along the same azimuth, or along different azimuths.

Occasionally, a relatively thick incompetent sub-surface formation is encountered, such as the formation 46 illustrated in FIG. 7. In this instance, two separate permeable masses 48, 50 may be placed in the formation 46 with the result that greater flow capacity is achieved. The coherent permeable masses 48, 50 may be physically separated or they may be abutted as shown in FIG. 7. In any event, positive placement of the packing material is achieved with the result that one or more coherent permeable masses are formed, through which the liquid or gaseous medium may be produced.

Although the invention has been shown in connection with certain specific embodiments, it will readily be apparent to those skilled in the art tha-t various changes may be made to suit requirements without departing from the spirit and scope of the invention.

We claim as our invention:

1. A method for consolidating an incompetent, fluid producing subsurface formation which is penetrated by a casing having a tube string descending therethrough to provide a conveying annulus and a packer carried by said tube string, comprising the steps of perforating said casing at vertically spaced locations to provide at least one small perforation and at least one large perforation both of which extend in-to said formation; setting said packer in the region between the perforations whereby one perforation communicates with said conveying annulus and the other perforation communicates with the interior of said 'tube string; circulating a washing liquid through one perforation, into said formation and out the other perforation to wash away a quantity of the particulate matter of said formation and create a cavity therein; pumping a liquid containing a permeable sealer member through said large perforation and into said cavity to lodge said permeable sealer member in said small perforation at a location externally of said casing, said permeable sealer member permitting efuX of said liquid therethrough; pumping a liquid containing particles coated with a settable coating, through said large perforation and into said cavity, said particles being of a size suficient to cause agglomeration thereof about said permeable sealer member so as to ll said cavity; and thereafter causing the settable coating of said particles to set and bond said particles into a coherent permeable mass which fills said cavity and through which the medium of said producing formation may ow while restraining motion of the particulate matter of said formation.

2. The method as defined in claim 1 including the additional steps of pump-ing a liquid containing an impermeable sealer member down said tube string to lodge said impermeable sealer member in said large perforation at a location internally of said tube string, and maintaining said impermeable sealer member lodged in said large perforation by fluid action until said settable coating of said particles has set.

3. The method as defined in claim 1 wherein the small and large perforations extend in diffe-rent directions whereby the cavity washed in said formation surrounds said casing.

4. The method as defined in claim 1 including the additional steps of perforating said casing at vertically spaced locations to provide at least one small perforation and at least one largen perforation both of which extend into said formation at new locations spaced from the location of the first formed perforations, and repeating the remaining steps to provide a second coherent permeable mass at a new location within said formation.

S. The method as dened in claim 1 wherein a plurality of small perforations and a plurality of large perforations `are formed in said casing, said perforations being positioned circumferentially about said casing; and wherein a plurality of permeable sealer members, one for each of said small perforations, are lodged in said small perforations whereby a torus-like coherent permeable mass, surrounding said casing is formed in said formation at the completion of the process.

References Cited UNITED STATES PATENTS 2,349,062 5/1944 Uren 166-15 3,088,520 5/1963 Hildebrandt 166-33 3,145,773 8/1964 lorda et al 166-27 3,294,168 12/1966 Bezemer et al 166-33 JAMES A. LEPPINK, Primary Examiner. 

1. A METHOD FOR CONSOLIDATING AN INCOMPETENT, FLUID PRODUCING SUBSURFACE FORMATION WHICH IS PENETRATED BY A CAUSING HAVING A TUBE STRING DESCENDING THERETHROUGH TO PROVIDE A CONVEYING ANNULUS AND A PACKER CARRIED BY SAID TUBE STRING, COMPRISING THE STEPS OF PERFORATING SAID CASING AT VERTICALLY SPACED LOCATIONS TO PROVIDE AT LEAST ONE SMALL PERFORATION AND AT LEAST ONE LARGE PERFORATION BOTH OF WHICH EXTEND INTO SAID FORMATION; SETTING SAID PACKER IN THE REGION BETWEEN THE PERFORATIONS WHEREBY ONE PERFORATION COMMUNICATES WITH SAID CONVEYING ANNULUS AND THE OTHER PERFORATION COMMUNICATES WITH THE INTERIOR OF SAID TUBE STRING; CIRCULATING A WASHING LIQUID THROUGH ONE PERFORATION, INTO SAID FORMATION AND OUT THE OTHER PERFORATION TO WASH AWAY A QUANTITY OF THE PARTICULATE MATTER OF SAID FORMATION AND CREATE A CAVITY THEREIN; PUMPING A LIQUID CONTAINING A PERMEABLE SEALER MEMBER THROUGH SAID LARGE PERFORATION AND INTO SAID CAVITY TO LODGE SAID PERMEABLE SEALER MEMBER IN SAID SMALL PERFORATION AT A LOCATION EXTERNALLY OF SAID CASING, SAID PERMEABLE SEALER MEMBER PERMITTING EFFLUX OF SAID LIQUID THERETHROUGH; PUMPING A LIQUID CONTAINING PARTICLES COATED WITH A SETTABLE COATING, THROUGH SAID LARGE PERFORATION AND INTO SAID CAVITY, SAID PARTICLES BEING OF A SIZE SUFFICIENT TO CAUSE AGGLOMERATION THEREOF ABOUT SAID PERMEABLE SEALER MEMBER SO AS TO FILL SAID CAVITY; AND THEREAFTER CAUSING THE SETTABLE COATING OF SAID PARTICLES TO SET AND BOND SAID PARTICLES INTO A COHERENT PERMEABLE MASS WHICH FILLS SAID CAVITY AND THROUGH WHICH THE MEDIUM OF SAID PRODUCING FORMATION MAY FLOW WHILE RESTRAINING MOTION OF THE PARTICULATE MATTER OF SAID FORMATION. 